The Liberal Democrats have won the Richmond Park by-election, pulling off one of most spectacular political upsets of recent years and denting the Conservatives’ narrow majority in the House of Commons.

The Lib Dem candidate Sarah Olney defeated former Conservative MP Zac Goldsmith, overturning his 23,000 majority, at last year’s general election, to win by 1,800 votes.

The by-election was called after Mr Goldsmith quit as a Tory MP in protest over plans to build a new runway at Heathrow airport.

However it swiftly became a vote about Britain’s decision to leave the European Union, which put Mr Goldsmith, who backed Brexit, at a disadvantage against Mrs Olney, a Remainer.

The LibDems’ victory – the party’s first by-election gain for a decade – means that the prospect of Prime Minister Theresa May calling an early general election next year is receding.

She told Sky News: “It does look now as if we can have a vote in Parliament that might override the referendum. And I will, obviously, be voting to Remain because that is always what I have believed.”

The result was a rejection of the “politics of anger and division”, she said: “We will defend the Britain we love. We will stand up for the open tolerant, united Britain we believe in.”

She said: “The people of Richmond Park and North Kingston have sent a shockwave through this Conservative Brexit government, and our message is clear: we do not want a hard Brexit. We do not want to be pulled out of the single market, and we will not let intolerance, division and fear win.”

A North Kingston resident for six years, Ms Olney is a qualified accountant and works at the National Physical Laboratory in Teddington. She is also chairman of North Kingston Liberal Democrats.

Pressed on the first things she will begin working on as an MP, she said: “Brexit and Heathrow were the two key things we fought this campaign on, so those are the two priorities when I get into parliament.”

Ms Olney said she now wanted Parliament to “override” the Brexit referendum.

Asked if she would actively resist Brexit as an MP, she said: “Absolutely. Now I’ve been given this mandate.”

Ms Olney said her dramatic victory was a rejection of the “Ukip vision” of Britain, and the politics of “anger and division”.

She told supporters: “The people of Richmond Park and North Kingston have sent a shockwave through this Conservative Brexit government, and our message is clear: we do not want a hard Brexit. We do not want to be pulled out of the single market, and we will not let intolerance, division and fear win.”

Jacob Rees-Mogg, the Eurosceptic Tory MP, told the Today programme that the by-election had been a verdict on Brexit by a constituency which voted to Remain at the last election.

Conservative Party: By-election result does not change Brexit

A Conservative Party spokesman said the result would make no difference to Brexit plans and offered “commiserations” to Mr Goldsmith.

He said: “Zac has been a strong and principled champion for the residents of Richmond Park and North Kingston over the past six years as their Member of Parliament, and a popular figure in the Conservative Party. We are sorry that he is no longer in the House of Commons.

“This result doesn’t change anything. The Government remains committed to leaving the European Union and triggering Article 50 by the end of March next year. In addition, we will continue to take decisive action in the national interest to secure the UK’s place the world – supporting a third runway at Heathrow to secure jobs and business opportunities for the next decade and beyond.”

The victory takes the LibDems’ MPs to nine in the Commons. Tim Farron, the Lib Dem leader who will visit the constituency today to mark the first big political win of his time as leader , said the “message is clear”.

He said: “The Liberal Democrats are back and we are carrying the torch for all of those who want a real opposition to this Conservative Brexit government.

“We are the only party fighting to keep Britain open, tolerant and united, and the only party that has said, loudly and proudly, that we want Britain to remain a member of the Single Market and that we want the people to be given the final say over the Brexit deal. That message has been resoundingly backed by the people of Richmond Park.”